Deduno (1-0) allowed four hits and didn't issue a walk for the Dominicans, who will close round-robin play Sunday against Puerto Rico after previously downing Venezuela in their Pool C opener.
Carlos Santana cracked a homer for the Dominicans.
Yoanner Negrin (0-1) took the loss for Spain, allowing five runs on three hits and four walks over 2 1/3 innings.
Spain lost 3-0 to Puerto Rico in its Friday opener.
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